1. Field of the Invention
The present invention relates to cleaning and disinfecting of a hemodialysis machine, and more particularly to an automated system therefor.
2. Description of the Prior Art
Hemodialysis machines are utilized by persons having insufficient or inoperative kidney functions. The machines may be used at a health facility or in the patient's home. The machine attaches the patient through an extracorporeal circuit of blood tubing to a dialyzer having a pair of chambers separated by a thin semi-permeable membrane. The patient's blood is circulated through one of the chambers. The hemodialysis machine maintains a constant flow of a dialysate through the second chamber. Excess water and wastes from the blood are removed by ultrafiltration through the membrane and carried out by the dialysate to a drain.
A typical hemodialysis machine provides a pair of hoses which connect to the dialyzer and include a source of incoming water, a filter and heater for bringing the water to a required temperature, a source of a dialysate which is introduced into the water in a predetermined concentration and necessary pumps, pressure regulators, a deaerator, flow controllers and regulators. When the machine is in use, the hoses are connected to the inlet and outlet ports of the dialyzer. After use, the hoses are removed from the dialyzer and connected to a bypass which couples the two hoses together. It is then necessary to clean the dialysate from the machine and the various tubes, hoses and other elements and to disinfect the various lines and parts of the machine.
Typical chemicals used for disinfection and cleaning are a 5.25% concentrated sodium hypochlorite solution, commonly referred to as "bleach", and a 37% formaldehyde solution, commonly referred to as "Formalin.sup.R ". In the cleaning and disinfecting procedure, it is necessary to first rinse the machine lines and parts with water to remove the dialysate and thereafter to cause either the bleach or formaldehyde to pass through the machine for predetermined times. After the disinfection operation, the solution must be thoroughly flushed out by means of a post-rinse.
Both of these chemicals are hazardous to the patient and the operator must be extremely careful not to inadvertently dialyze with either of these two chemicals remaining in the system. Although some apparatus may have safety devices which require certain conductivity of the dialysis, there are occasions in which improper concentrations have been used and serious injury or death to a patient has occurred.
A typical prior art procedure for disinfection will be described using a hemodialysis machine available from Travenol Laboratories, Inc. of the SPS 450 series. In this machine, an external line known as the concentrate line is normally connected to a source of dialysate concentrate which is mixed with the incoming warm water by means of a proportioning pump to produce the required dialysate solution. When the machine is to be cleaned and disinfected, the concentrate line is removed from the dialysate concentrate container and connected to a water rinse port of the machine. The hoses to the dialyzer are disconnected therefrom and connected together through a bypass or interlock port. The machine is operated for a preselected rinsing period which cases the incoming water to be circulated through the concentrate line, the proportioning pump, and the other lines and elements of the machhine which flushes the dialysate out through the drain.
After the required prerinsing period, the operator now introduces the bleach or formaldehyde solution. Generally, this material is poured into an open cap. About 140-160 mls of the material is required. The operator removes the concentrate line from the water rinse port and drops the end thereof into the cup. The machine is then operated for a specified disinfect period during which the proportioning pump draws the bleach or formaldehyde from the cup and introduces it into the water circulating through the system. The proportioning will be the same as that for which the proportioning pump is set for dialysis; for example, a ratio of 34 parts of water to one part of concentrate is commonly used. The operator must be careful to determine when the container of bleach or formaldehyde is nearly empty since the drawing of air into the machine is undesirable.
After passing a preselected volume of bleach or formaldehyde through the system for the selected period of time, the concentrate line is again connected manually to the water rinse port and the machine is operated in a post-rinse mode using water to thoroughly flush out all of the disinfecting liquid. When using bleach, which is essentially a cleaning procedure, the post-rinse can follow immediately after the treatment with the disinfect cycle. However, the procedure requires that formaldehyde be ingested into the machine, the machine turned off and stored within the system for at least two hours. In general practice, the use of formaldehyde is limited to the last operation of the day with the apparatus and the formaldehyde allowed to stand in the machine overnight. After the formaldehyde storage period, the post water rinse is accomplished to remove the residual formaldehyde. Some users will have apparatus to test the residual formaldehyde until it is less than about 10 parts per million.
As will be recognized, a significant amount of labor is required on the part of the operator to perform a disinfection procedure. The operator must monitor the apparatus and, since some of the periods require 10 to 30 minutes, there is a significant cost for this labor. Furthermore, the handling of these relatively dangerous materials in open containers provides several opportunities for spillage, which can be dangerous to the operator and can produce undesirable fumes. If the proper rinse times and storage times are not strictly observed, there is always the danger of leaving residual bleach or formaldehyde in the system such that a risk exists with respect to the next patient undergoing dialysis on the machine.
As may be recognized, there is a long felt need for an automated hemodialysis machine cleaning and disinfecting system that will automatically and accurately time the cycle of events, that will obviate the need for open containers, that will reduce the labor required for the operation, and that will increase the safety of the process. Furthermore, such a system would perform its function in a more uniform manner, with more predictable results, and eliminate the potential for disinfectant to be introduced into the machine during dialysis.